Accessor for a reference to a hash where the keys are the names of the foreign keys and for each foreign key,
the value is a hash reference having as keys the names of the referenced columns and as values the names of the referencing columns,
externally read-only.

Accessor for a reference to a hash where the keys are the names of the foreign keys and for each foreign key,
the value is a reference to an array containing the column names of the referenced columns,
externally read-only.

Accessor for a flag which is set to true only if the caller wants to handle a self-reference (i.e.
if handle_self_ref_wanted is true) and it has been determined that a self-reference exists,
externally read-only.

Accessor for a reference to a hash where,
assuming there is a self-reference,
each keys is the id of a parent record and the corresponding value a reference to an array containing the list of client node ids.
If no self-reference exists,
the value is undef.
This accessor is externally read-only.

Internal method.
Returns a reference to a dictionary having as keys the fkey names and for each key as value a dictionary where the keys are the names of the referenced column names and the values the names of the corresponding referencing column names.